Effects of inter-granular Sn on transport and magnetic properties of polycrystalline GdBCO superconductors

Inter-granular Sn particles affect transport and magnetic properties both in the normal and superconducting states of polycrystalline GdBa₂Cu₃O_7−δ (GdBCO) superconductors drastically. Normal state resistivity at 300 K increases ~ 18.0 times as the concentration of Sn is increased. An unusual upturn in resistivity as a function of temperature curve with a dip is observed in GdBCO with 3.0 wt% of Sn in which suppression of superconducting phase transition has been observed. Current-voltage (IV) curves below T_c exhibit nonlinear features in composites of GdBCO and Sn. Magnetization (M) as a function of magnetic field (H) curves at 2.0 –20.0 K in GdBCO shifts strongly with the addition of 1.0 wt% Sn. We have extracted irreversible magnetization, lower critical field (H_c1) and magnetic critical density (J_cm) as a function of H at several T. The maximum pinning force density is 0.4 GN/m³ in GdBCO which is reduced in the Sn added GdBCO.